Antenna with built-in filter

Abstract

At least one filter block (25, 35, 45) is formed in a thin and flat dielectric multilayer structure (21) and fixed with radiation elements (2, 3). Each filter block includes at least one of a low-pass filter, a high-pass filter and a band-eliminating filter. On the surface (one major surface) side and/or the side face of the multilayer structure, at least one radiation element (2, 3) being connected with the filter block is provided and feeding parts (28, 38, 48) for supplying signal to the radiation elements are provided on the rear surface of the multilayer structure. Consequently, the antenna and the filter block are integrated and a small surface mountable antenna with a built-in filter of a structure such that signals are not mixed each other even when signals of a plurality of frequency bands are transmitted/received can be obtained.

Description

[0001]This application is the National Phase of International Application PCT / JP02 / 01637 filed Feb. 22, 2002.TECHNICAL FIELD[0002]The present invention relates to an antenna with a built-in filter which has a filter having a superior separating function so as not to generate a noise on another signal because of reciprocal interference even when a plurality of frequency bands are transmitted or received at the same time, and which is small in size so as to be suitable for being mounted on a portable telephone, a personal digital assistant or the like, and in which matching is easy. More particularly, it relates to an antenna with a built-in filter having a compact structure in which reciprocal interference will not occur even if it is constituted such that signals of a plurality of frequency bands such as cellular and GPS or Bluetooth can be transmitted or received by one block of antenna.BACKGROUND ART[0003]Conventionally, signals transmitted or received by an antenna pass through a...

AI Technical Summary

Benefits of technology

[0032]One antenna element is folded so that at least two portions in which adjacent elements are electrically coupled respectively are formed, the radiation electrode is formed from the antenna element so as to resonate in the desired four frequency bands by adjusting the electrically coupled portion and so that one end of the antenna element is connected to filters of the respective frequency bands through a multiplexer. As a result, the one radiation electrode is provided for four frequency bands of cellular, GPS and BT, thereby to miniaturize it with further simple structure.

[0033]The dielectric multilayer structure according to the present invention is the dielectric multilayer structure in which the plural dielectric sheets each having an electroconductive

Problems solved by technology

However, a signal transmission path is locally narrowed in the connection using the through-hole, which increases high-frequency resistance or inductance and comes to increase in transmission signal loss or decline in the damping characteristic.

Although the structure can be shielded in the vertical direction by providing an earth conductor film on the ceramic sheet, the shielding is not effective in the surface direction of the multilayer structure (in the direction parallel to the ceramic sheet) because an electric wave is leaked laterally from a gap of the connecting parts of the through-hole.

However, since further miniaturization is demanded in the portable device, to provide the antennas at various places in the portable device is contrary to the demand for the miniaturization.

As described above, according to the conventional antenna with a built-in filter, since the antenna and the band pass filter are connected through the connector and connection cable, the device becomes large and loss is increased.

In addition, since the radiation element and the filter separately function, it is necessary to match the impedance of the radiation element, which furthe

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